The invention relates to a medical/technical tool holder apparatus with torque limitation in accordance with the preamble of claim 1. The invention further relates to a shear body for a medical/technical tool holder apparatus with torque limitation in accordance with the preamble of claim 14. The invention further relates to a kit for a medical/technical tool holder apparatus with torque limitation in accordance with the preamble of claim 19.
A large number of torque transmitting couplings which transfer only a limited torque is known from mechanics. Couplings of this kind are also designated as overload couplings.
Disadvantageous in couplings of this kind is that they are not suitable for medical/technical uses, for example when built into instruments for surgical operations in humans, since the maximum torque which can be achieved is relatively imprecise, and the maximum torque which can be achieved is subject to long-term changes.
The object of the present invention is to create a medical/technical tool holder apparatus with torque limitation which has a relatively exact maximum torque, with the maximum torque being reproducible even in the long run, for example after multiple steam sterilizations.
This object is satisfied by a medical/technical tool holder apparatus with torque limitation having the features of claim 1. Subordinate claims 2 to 12 relate to further, advantageous embodiments of medical/technical tool holder apparatuses with torque limitation. The object is further satisfied by a shear body in accordance with claim 14, which is designed to be adapted for use in the medical/technical tool holder apparatus in accordance with the invention. Subordinate claims 15 to 18 relate to further advantageously designed shear bodies.
The object is satisfied in particular by a medical/technical tool holder apparatus with torque limitation which comprises a receiver for at least one shear body and a shearing means which is rotatably connected to the receiver and which is arranged relative to a shear body located in the receiver in such a manner that the shearing means contacts the shear body at least when a torque acts on the shearing means, with the shearing means and the shear body being mutually matched and arranged in such a manner that the shearing means at least partly severs the shear body when a specific torque is exceeded.
In a preferred embodiment, the medical/technical tool holder apparatus in accordance with the invention is connected on the one side to a handle and on the other side to a tool and forms in this manner a medical/technical instrument, for example a surgical instrument. In a preferred embodiment the handle is designed to be elongate and in this defines a longitudinal axis about which the instrument is rotated together with the tool, with the tool holder apparatus, which is arranged between the handle and the tool, limiting the maximum torque to be transmitted. For greater torques, for example for torques greater than 5 Nm, the handle can also be designed as a T-grip.
The medical/technical tool holder apparatus in accordance with the invention has the advantage that the maximum torque which can be transmitted can be relatively precisely defined through the use of a shear body in combination with a shearing means. The shear body is destroyed through the action of the shearing means and must be replaced after the use of the tool holder apparatus. The shearing means has a low wear and can, where appropriate, likewise be replaced. The medical/technical tool holder apparatus in accordance with the invention therefore has the advantage that the maximum torque which can be transmitted is relatively exactly reproducible over a relatively long time interval of, for example, a year or even several years. In addition no calibration of the tool holder apparatus is required.
The shearing means come into contact with the shear body at the latest when the handle is rotated, with the shearing means penetrating into the shear body with increasing torque and partly or completely severing it when a specific torque is exceeded. A severed shear body is destroyed and must be replaced. In an advantageous embodiment the tool holder apparatus in accordance with the invention has a receiver for a plurality of shear bodies, for example a receiver for six shear bodies, so that the shear body is severed a number of times in succession when a specific torque is exceeded, but the shear bodies must be replaced only when all shear bodies located in the instrument have been destroyed.
The medical/technical tool holder apparatus in accordance with the invention enables for example a screw such as a stud screw or a bone screw to be tightened with a precisely pre-set torque during implanting.
The tool holder apparatus in accordance with the invention has the advantage that maximum torques of different magnitude can be pre-set depending on the requirement. The maximum torque for the severing of a shear body is determined by:
the material properties of the shear body,
the geometrical design of the shear body,
the geometrical design of the shearing means, with the shearing means preferably having a blade, the geometry of which can be designed in a large number of shapes,
the effective lever arm of the shearing means,
the degree of the severing of the shear body, partial or complete.
Through a suitable combination of these parameters, a large number of different and precisely reproducible maximum torques can be achieved. In a preferred embodiment the same shearing means is always used, with shear bodies having different material properties and/or different geometrical designs being used, so that the maximum torque amounts to, for example, 4 Nm, 6 Nm or 10 Nm, depending on the respective shear body. In a preferred embodiment these shear bodies have a color coding, with shear bodies of the same color yielding the same maximum torque. The tool holder apparatus in accordance with the invention thus has the advantage that the maximum torque achievable can be varied within a broad range using the same apparatus, in which a corresponding shear body is inserted into the receiver depending on the required maximum torque. Especially in the implanting of an orthopedic implant such as a hip joint pan, the maximum permissible torque can depend, for example, on the size of the implant chosen. The tool holder apparatus in accordance with the invention enables a surgeon or an assistant to set the maximum torque of the instrument during an operation by the corresponding shear bodies being inserted into the receiver. A set of different shear bodies must be available in sterilized form for this.
A surgical instrument comprising the medical/technical tool holder apparatus in accordance with the invention can, for example, be designed as a torque limitation screwdriver.
The medical/technical tool holder apparatus in accordance with the invention is manufactured of a sterilizable material, in particular metal, in a preferred embodiment, so that the shear body can be removed from the apparatus after an operation, the apparatus is sterilized and can then be used for further operations.
The tool holder apparatus in accordance with the invention can be assembled for a great variety of release moments without altering the external geometry of the tool holder apparatus or of the shear pin. The tool holder apparatus in accordance with the invention can be assembled in a module-like way taking into account the respective release moment required so that an instrument having the required release moment is available with a few changes, for example replacing a single blade with a double blade, or by the use of a blade with a sharp or blunt form.